1. Field of the Invention
This invention relates to a machine for bending a small-diameter metallic conduit at several points and more particularly, to a small-diameter metallic conduit bending machine adapted to shape a metallic conduit whose individual bend sections differ in the bend direction three-dimensionally from one another, not lying on the same plane, such as the fuel pipeline or brake pipeline of a car.
2. Description of the Prior Art
A conventional bending machine of the foregoing type includes a required number of bending units disposed correspondingly to a plurality of bend portions, each bending unit being configured as shown in FIG. 9 so that with respect to each bending work, a receiving roll 11 is moved by a cylinder 12 to come into contact with a metallic conduit 13, and then a bending roll 14 is moved by another cylinder 15 to bend the metallic conduit 13. In this drawing, 16 and 17 are mounts, 18 and 19 are stays, and 20 is a base.
According to the foregoing conventional bending machine, however, since the bending work is carried out by moving the receiving roll 11 and the bending roll 14 by means of the respective cylinders 12 and 15, each bending work needs two actions, thus, the machining time is long. Further, since the bending work is completed when the piston rods of both cylinders 12 and 15 reach their extended state, upon supply of a pressurized fluid into the cylinder ( generally, an air cylinder ) at the time of bending, the bending moment imposed on the piston rod increases, and flexure resulting from the reaction caused at the time of bending appears in the stays 18 and 19 and the mounts 16 and 17 for supporting the cylinders 12 and 15; consequently, a minute discrepancy ( called "breathing" by those skilled in the art ) appears between the receiving roll 11 and the bending roll 14, thereby resulting in variations in products. To eliminate such discrepancy, it is necessary to make the stays 18 and 19 and the mounts 16 and 17 thick and rigid. If designed so, however, the machine becomes large-sized and heavy ( but, in spite of such provisions, some discrepancy could not be eliminated ). Further, since the machine as a whole is necessary to be designed and composed while giving consideration to the position, orientation, etc. of each of the cylinders 12 and 15, receiving roll 11 and bending roll 14, a long time is required for its manufacture, such as assembly and adjustment; accordingly, the machine in the prior art sometimes could not be put in service in time where the starting of mass production was set. Other problems of the prior art are that parts and moving portions are numerous, the manufacturing cost is very high, and the durability is poor.